Jointed body of glass-ceramic and aluminum nitride sintered compact and method for producing the same

ABSTRACT

A compact, low electric resistance and high heat-spreading electric circuit substrate, which is suitable for an electric circuit used at microwave of 1 GHz or more as used in the field of wireless communication such as portable telephones or optical communication, is provided. Also provided is a joined body of glass-ceramic with aluminum nitride sintered body, the glass-ceramic containing crystals having the strongest line in the range of 2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line, e.g., anorthite crystals, and having a composition containing 0.5-30 mass % of Zn component in terms of oxide, not more than 10 mass % in total of Ti component and Zr component in terms of corresponding oxides and not more than 5 mass % of Pb component in terms of oxide. The joined body is prepared by forming a layer of amorphous glass of above composition on an aluminum nitride sintered body, and thereafter heating the composite at temperatures not lower than the softening point of the amorphous glass, e.g., 600-1100° C., and concurrently crystallizing the same by said heating.

TECHNICAL FIELD

This invention relates to a jointed body of glass-ceramic and aluminumnitride sintered body and method for producing the jointed body.

BACKGROUND ART

Recently, use of microwave of 1 GHz, such as microwave band andquasimillimetric wave band, is increasing in the field of wirelesscommunication, e.g., portable telephones, and optical communication.

As semiconductors operated in such a high-output, high-power consumptionGa—As FET, Si—Ge HBT, CMOS or GaN laser diode and the like are startedto be used. Electric circuits on which such semiconductors are to bemounted must meet such requirements as 1) that the circuit patternmaterial shows small electric resistance, 2) that multi-layered circuitcan be formed for size reduction, 3) that the substrate insulationmaterial has a high heat conductivity, high electric insulation anddesirably low dielectric constant, and 4) that environmental pollutionby circuit substrate material is little.

However, there is no single insulating substrate material meeting all ofthese conditions. Multi-layered circuit substrate using a highlythermoconductive aluminium nitride sintered body is available, but itselectric circuit conductor is made of tungsten/molybdenum type materialhaving high electric resistance and is unsuitable for high-frequencycircuits.

A conceivable realistic solution of above problem is a composite circuitsubstrate in which aluminum nitride sintered body is joined with glass.That is, aluminum nitride sintered body functions to spread the heatfrom semi-conductors, and further in which a part of an electric circuitis formed; a mono-layered or multi-layered glass layer is formed thereonusing paste-printing technique or the like: and an electric circuit isformed with Au-, Ag-, or Cu-derived low resistance material on thesurface or inside of said glass layer.

A glass material for realizing such a circuit substrate must possesssuch properties as: 1) high electrical insulation and favorabledielectric characteristics, 2) thermal expansion coefficient close tothat of aluminum nitride sintered body, 3) direct jointability withaluminum nitride sintered body, not mediated by an oxide film, 4)inclusion of crystallized phase to enable repeated sintering, and 5)relatively low jointing temperature with aluminum nitride sintered body,which must not be higher than the melting point of the metal componentof Au-, Ag- or Cu-metallized material, specifically, not higher than1100° C., in other words, the operation temperature for softening theglass to achieve sufficiently intimate jointing with aluminum nitridesintered body must not be higher than 1100° C.

As low temperature-softening glass, those containing lead oxide can beproduced with relative ease, but lead-containing glass is fundamentallytoxic and significantly adversely affects terrestrial environments,although lowering in softening point can be easily achieved therewith.Furthermore, lead-containing glass is apt to have a high thermalexpansion coefficient. It also has a defect of readily inducing foamingphenomenon under high temperatures at which it reacts with aluminumnitride sintered body and the reaction gas remains in the glass.

As glass materials for the circuit substrates, those which are describedin JP-A-340443/1994 and JP-B-68065/1995 are known. The glass inJP-A-340443/1994 contains a large amount of titanium or zirconium andlead, and the defect of higher thermal expansion coefficient than thatof aluminum nitride sintered body, which is 4.5×10⁻⁶/° C., is not fullyremoved. The glass also exhibits low joining strength with aluminumnitride substrate. The glass in JP-B-68065/1005 exhibits favorablethermal expansion coefficient and electric insulation, but requires ahigh temperature treatment at 1100-1500° C. for obtaining satisfactoryjointability with aluminum nitride. Therefore, two or more steps arenecessary for incorporating an electric circuit therein.

The present invention is made for solving such problems asabove-described. I noticed an anorthite (CaO.Al₂O₃.2SiO₂) sintered bodyhas, as taught in an article by R. A. Gdula, American Ceramic SocietyBulletin, 1971, Vol.50, No.6, 555-557, a high electric insulation(2.8×10¹⁵ Ω.cm: 25° C.), a small dielectric constant (6.2: 1 MHz, 25°C.), a thermal expansion coefficient (48×10⁻⁷/° C.: 150° C.-700° C.)which is close to that of aluminum nitride sintered body, andfurthermore stability in reducing atmosphere such as of H₂, andconducted concentrative studies thereof.

In consequence, I discovered amorphous glass which contains Ca, Si andAl components and hence is expected to be crystallized into anorthitecrystals under heating has low melting point in the absence of a largeamount of Pb component, exhibits good jointability with aluminum nitridesintered body at relatively low temperatures not higher than 1100° C.and crystallizes under heating to separate a crystal component having acharacteristic strongest line in a range of 2Θ=27.6°-28.2° in powderX-ray diffraction using CuKα line. Moreover, I also found that thecrystallized glass or glass-ceramic containing said crystal componentpossessed not only those characteristic properties attributable to saidanorthite sintered body but also high thermal stability wellwithstanding repeated heating for forming a multi-layered glass. (In thefollowing, an amorphous glass having the composition as will form thecrystals showing the strongest line in a range of 2Θ=27.6° to 28.2°under heating may occasionally be referred to as “starting glass”.

I furthermore found that use of Zn component-containing glass as thestarting glass could further lower the crystallization temperature ofthe crystals having the strongest line in a range of 2θ=27.6° to 28.2°in powder X-ray diffraction using CuKα line, by 25-100° C. or even more,and could also sharpen the separation pattern of said crystals. It waswhereby made possible to prepare a jointed body of glass-ceramic withaluminum nitride sintered body at still lower temperatures, with lessoccurrence of swelling or residual. carbon in so produced glass-ceramic.

Moreover, I also found that a glass of above-described composition couldbe sufficiently crystallized, without containing a large amount of Ti orZr component as nucleating agent and hence the glass-ceramic preparedtherefrom could have a thermal expansion coefficient nearly the same tothat of aluminum nitride sintered body.

DISCLOSURE OF THE INVENTION

Namely, the present invention provides a jointed body of glass-ceramicconsisting of crystalline portion and amorphous portion with aluminumnitride sintered body, which is characterized in that the crystallineportion contains as main crystals a crystal having the strongest line ina range of 2θ=27.6° to 28.2° in powder X-ray diffraction using CuKα lineand said glass-ceramic contains 0.5-30% by weight of a Zn component interms of oxide, not more than 10% by weight of the sum of a Ti componentand Zr component in terms of respective oxides and not more than 5% byweight of a Pb component in terms of oxide.

The invention also provides a method for producing a jointed body ofglass-ceramic with aluminum nitride sintered body, which method ischaracterized by forming a glass layer containing an amorphous glasshaving a composition of 0.5-30% by weight of a Zn component in terms ofoxide, not more than 10% by weight of the sum of a Ti component and Zrcomponent in terms of respective oxides and not more than 5% by weightof a Pb component in terms of oxide, on an aluminum nitride sinteredbody, heating the resulting composite to a temperature not lower thanthe softening point of said amorphous glass and whereby crystallizingsaid glass to convert it to a glass-ceramic, the main crystals thereinhaving the strongest line in a range of 2θ=27.6° to 28.2° in powderX-ray diffraction using CuKα line. The present invention also covers anembodiment of the method for producing the jointed body in which, inaddition to the glass-ceramic and aluminum nitride sintered body, anelectric circuit layer is jointed by heating.

The invention furthermore provides a glass-ceramic composed of amorphousportion and crystalline portion, which can be favorably used in saidjointed bodies and the like, said crystalline portion containing as maincrystals a crystal having the strongest line in the range of 2θ=27.6° to28.2° in powder X-ray diffraction using CuKα line, and saidglass-ceramic being composed of 8-25% by weight of CaO, 15-35% by weightof Al₂O₃, 33-55% by weight of SiO₂, 0.05-18% by weight of B₂O₃ and0.5-25% by weight of ZnO.

The glass-ceramic constituting the jointed body of the present inventionconsists of crystalline portion and amorphous portion.

Compounds consisting solely of crystalline portion have excessively highsoftening points, and are very difficult to be jointed with aluminumnitride sintered body. Glass-ceramic containing amorphous portion can bejointed with aluminum nitride sintered body at relatively lowtemperatures, but it is extremely difficult to completely eliminate theamorphous portion by 100% crystallization. On the other hand, glassconsisting solely of amorphous portion has a high thermal expansioncoefficient and is inferior in electric characteristics and chemicalresistance.

Said crystalline portion contains a crystal having the strongest line ina range of 2θ=27.6° to 28.2° in powder X-ray diffraction using CuKα line(which crystal may hereafter be referred to as “A crystal”) forming themain crystal phase. A typical example of such a crystal component is, asillustrated by FIG. 1, anorthite crystal (CaO.Al₂O₃, 2SiO₂; CaAl₂Si₂O₈)which is identified as Powder Diffraction File No. 20-20 of JCPDS (JointCommittee On Powder Diffraction Standards).

When main crystals separated are those (A crystals) having the strongestline in a range of 2θ=27.6° to 28.2° in powder X-ray diffraction usingCuKα line, the following effects can be achieved. That is, anorthitecrystal which is a typical A crystal as aforesaid has high electricinsulation and small dielectric constant, and hence exhibits excellentelectric characteristics as a substrate for electric circuits. Alsobecause its thermal expansion coefficient is close to that of aluminumnitride, that of the glass-ceramic as a whole can also be made of samelevel with aluminum nitride sintered body with ease. Anorthite crystalis stable under heating in a reducing atmosphere, which renders itsrepeated heating possible, for forming a multi-stratified glass layer.Moreover, chemical resistance of the glass layer also is drasticallyimproved compared to amorphous glass.

When a Zn component is blended in a starting glass, depending on theheating conditions crystals having the strongest line in a range of2θ=36.6° to 37.0° in powder X-ray diffraction using CuKα line (whichcrystal may be hereafter referred to as “B crystal”) may be separated,besides A crystals, as the crystalline portion of the glass. A typicalexample of B crystal is gahnite crystal (ZnO, Al₂O₃, 2SiO₂; ZnAl₂O₄)which is identified as Powder Diffraction File No. 5-669 of said JCPDS.

In crystalline portion of the glass-ceramic following the presentinvention thus A crystals having the strongest line in a range of2θ=27.6° to 28.2° in powder X-ray diffraction using CuKα line areseparated, and B crystals having the strongest line in a range of2θ=36.6° to 37.0° using powder X-ray diffraction using CuKα line mayalso be separated. Whereas, according to the present invention Acrystals must be the main crystals, because while anorthite crystalwhich is the representative of A crystal has a thermal expansioncoefficient of 4.8×10⁻⁶/° C., a value close to that of aluminum nitridesintered body, gahnite crystal which is the representative of B crystalhas a high thermal expansion coefficient of 7.7×10⁻⁵/° C., and where Bcrystal content is high, it becomes very difficult to make thermalexpansion coefficient of the glass-ceramic equivalent to that ofaluminum nitride sintered body. Here “main crystals” signifies that theamount of A crystals as determined following the later specified methodfor measuring crystallization amount is at least 50% by weight,preferably at least 60% by weight, inter alia, at least 70% by weight ofthe crystalline portion.

Separation of B crystals, on the other hand, is not essential, butpreferably B crystals occupy 10-40% by weight, preferably about 10-30%by weight, of the crystalline portion. There is a tendency that the moreB crystals, the more A crystals. However, excessively high B crystalcontent is objectionable because it has a higher thermal expansioncoefficient than A crystal.

It is sufficient for the glass-ceramic following the present inventionthat the total amount of crystals is of the level allowing confirmationby powder X-ray diffraction using CuKα line. Whereas, from the viewpointof thermal expansion coefficient, electrical characteristics, durabilityand softening point, total amount of A crystals and B crystals asdetermined by the later specified measurement method of crystallizationis preferably 1-90% by weight; in particular, 3-85% by weight, interalia, 30-80% by weight. The best result can be obtained when it is40-70% by weight. Glass of high crystal content tends to require hightemperatures for its production or fail to give sufficient jointingstrength with aluminum nitride sintered body. On the other hand, thereis seen a tendency that the less the crystal content, the higher thethermal expansion coefficient and the lower the electricalcharacteristics, chemical resistance, durability, etc.

It is preferred that the total crystalline portion is 30-80% by weight,of which 60-90% by weight being A crystals and 10-40% by weight being Bcrystals. Even better is that the total crystalline portion is 40-70% byweight, of which 70-90% by weight being A crystals and 10-30% by weightbeing B crystals.

So long as the effects of the present invention are not impaired,crystal(s) other than one having the strongest line in the ranges of2θ=27.6° to 28.2° and 2θ=36.6° to 37.0° in powder X-ray diffractionusing CuKα line, may be separated.

The respective amounts of A crystals and B crystals in a glass-ceramicfollowing the present invention can be determined by the followingmethod, which is explained referring to anorthite, a typical example ofA crystal, and gahnite, a typical example of B crystal.

First, the end point of crystallization is ascertained by means ofpowder X-ray diffraction and differential thermal analysis. Where anamorphous glass is heated to be crystallized, until the condition isreached at which the crystallization no more progresses even underhigher temperatures or longer hours' heating. That condition isspecified as the one at which the maximum anorthite and gahnite contentsare attained. The intensity ratio between the strongest lines ofanorthite and gahnite in powder X-ray diffraction (when CuKα line isused, the strongest line of anorthite appears in the range of 27.6° to28.2°, and that of gahnite, in the range of 36.6° to 37.0°) is recordedas the molar ratio of anorthite crystal to gahnite crystal (the molarratio is hereafter called R). Then, of the components contained in theglass-ceramic of the present invention, Al₂O₃ which is a constituent ofboth anorthite crystal and gahnite crystal is distributed to said twoaccording to R. Where no gahnite crystal is present, it is unnecessaryto distribute the Al₂O₃, but all is calculated as anorthite crystalcomponent.

Then the maximum amount of crystallization in the glass-ceramic iscalculated. For calculating the maximum amount of anorthite, the leastcomponent among those constituting anorthite, i.e., CaO, Al₂O₃ and SiO₂,in terms of molar ratio is taken as the standard, under a presumptionthat all of the least content component is consumed for crystallizationof anorthite and the remaining two components are consumed at a molarratio of CaO: Al₂O₃:SiO₂=1:1:2 to form anorthite crystals, and the totalamount of CaO, Al₂O₃ and SiO₂ at this time is the maximum amount ofseparated anorthite crystals as referred to in the present invention.According to the present invention, furthermore, the Al component iscalculated by a unit of Al₂O₃, and the Al₂O₃ content used in the abovecalculation is same as the calculated amount as distributed to anorthiteaccording to R as above-specified.

On the other hand, calculation of the maximum amount of gahnite crystalsis based on the less component between those constituting gahnite, i.e.,ZnO and Al₂O₃, in terms of molar ratio, under a presumption that all ofthe least content component is consumed for crystallization of gahniteand that the other component is consumed at a molar ratio ofZnO:Al₂O₃=1:1 to form gahnite crystals. The total amount of ZnO andAl₂O₃ at this time is the maximum amount of gahnite crystals as referredto in the present invention. The Al₂O₃ content used in this calculationis the same to that which is distributed to gahnite crystals accordingto R as above-specified.

For example, taking a case of a glass containing CaO: 15 wt % (2.68mmol/g), Al₂O₃: 24 wt % (2.35 mmol/g), SiO₂: 42 wt % (7.00 mmol/g),B₂O₃: 8 wt % (1.14 mmol/g) and ZnO: 11 wt % (1.36 mmol/g), itscrystallization from amorphous condition is deemed to be completed byheating at 900° C. The ratio (R) of anorthite to gahnite in theglass-ceramic after said heating at 900° C. is 0.3769.

Then the Al₂O₃ content of 24 wt % (2.35 mmol/g) is distributed accordingto R=0.3769, i.e., 17.43 wt % (1.71 mmol/g) to anorthite crystals and6.57 wt % (0.64 mmol/g) to gahnite crystals.

The glass composition capable of separating anorthite crystals is CaO:15 wt % (2.68 mmol/g), Al₂O₃: 17.43 wt % (1.71 mmol/g) and SiO₂: 42 wt %(7.00 mmol/g), and therefore the maximum amount of anorthite crystals iscalculated following the content of Al₂O₃, the least component, to bethe sum of CaO: 9.58 wt %, Al₂O₃: 17.43 wt % and SiO₂: 20.54 wt %, whichequals 47.55 wt %.

Because ZnO: 11 wt % (1.36 mmol/g) and Al₂O₃: 6.57 wt % (0.64 mmol/g),the sum of ZnO: 5.24 wt % (0.64 mmol/g) and Al₂O₃: 6.57 w % (0.64mmol/g) which equals 11.81 wt % is the maximum amount of gahnitecrystals.

Hence, the maximum crystal content in this glass-ceramic, anorthitecrystals and gahnite crystals, as combined is 59.36 wt %.

The remaining CaO: 5.42 wt %, SiO₂: 21.46 wt %, ZnO: 5.76 wt % and B₂O₃:8 wt % are calculated to form amorphous glass matrix.

A crystal content in a glass-ceramic can be calculated from the maximumcrystal content as calculated by the above method, X-ray diffractionintensity and measured X-ray diffraction intensity.

For example, starting from a starting glass composed of above componentsand which is in amorphous condition, its heating temperature iscontinuously raised until its anorthite and gahnite crystal contentsreached the maximum. At that time the powder X-ray diffraction intensity(count number) indicated by the strongest line inherent in anorthitecrystal is 1170, and that (count number) indicated by the strongest lineinherent in gahnite crystal is 441.

Where said X-ray diffraction intensity (count number) of the startingglass under heating, in which anorthite crystals alone are separated, is55, the anorthite crystal content of the glass under heating iscalculated to be 2.24 wt % (47.55×55/1170=2.24).

When gahnite crystals also start to be separated under further heatingand X-ray diffraction intensity (count number) of the gahnite crystalsis 90, the gahnite crystal content in the glass-ceramic under saidcondition is calculated to be 2.41 wt % (11.81×90/441). If the X-raydiffraction intensity of anorthite crystals in the glass containing 2.41wt % of gahnite crystals and being heated is 1116, the anorthite crystalcontent of the glass-ceramic is calculated to be 45.36 wt %, and thecrystal content, which is the sum of said anorthite crystals and gahnitecrystals, of the glass-ceramic is 47.77 wt %.

In the aforesaid glass under heating in which anorthite crystals aloneare separated in an amount of 2.24 wt %, its crystalline portionconsists of CaO: 0.45 wt %, Al₂O₃: 0.82 wt % and SiO₂: 0.97 wt %. Thecomposition of the amorphous portion is: CaO: 14.55 wt %, Al₂O₃: 23.18wt %, SiO₂: 41.04 wt %, B₂O₃: 8 wt % and ZnO: 11 wt %.

Also in the glass wherein 45.36 wt % of anorthite crystals and 2.41 wt %of gahnite crystals are separated, the anorthite crystal portionconsists of CaO: 9.14 wt %, Al₂O₃: 16.62 wt % and SiO₂: 19.59 wt %; andthe gahnite crystal portion consists of Al₂O₃: 1.34 wt % and ZnO: 1.07wt %. The amorphous portion contains CaO: 5.86 wt %, Al₂O₃: 6.04 wt %,SiO₂: 22.41 wt %, B₂O₃: 8 wt % and ZnO: 9.93 wt %.

Where A crystal and B crystal are other than anorthite and gahnite,respectively, their compositions can be determined in a manner similarto the above-described method.

Glass-ceramic containing anorthite crystals, which is to be used in thepresent invention, normally contains Ca, Al and Si. These components areconsidered to be crystallized as anorthite crystals to show thestrongest line appearing in powder X-ray diffraction using CuKα line inthe range of 2θ=27.6°-28.2°. These components may also be present in theamorphous portion.

Ca component is preferably contained in glass-ceramic in an amount asconverted to CaO of 5-25 wt %, in particular, 8-25 wt %. Where the Cacontent is too low, it becomes difficult to separate crystals which areinferred to be anorthite crystals in glass-ceramic. On the other hand,when the amount is excessive, jointability of the glass-ceramic withaluminum nitride sintered body is impaired, e.g., cracks are formedduring the jointing operation.

Preferred Al component content in terms of Al₂O₃ is 15-40 wt %, inparticular, 15-35 wt %. Where the Al component content is too low,anorthite crystals are difficult to be separated, but when it is toomuch, there observed a tendency that high temperatures are required forjointing with an aluminum nitride sintered body.

Too low a Si component content also renders it difficult to separateanorthite crystals. Conversely, when it is too high, higher temperaturestend to be required for jointing the glass-ceramic with aluminum nitridesintered body. Si component content is preferably 25-60 wt % in terms ofSiO₂, in particular, 33-55 wt %.

It is important that glass-ceramic according to the present inventioncontains Zn component. By incorporating a Zn component, it becomespossible to lower the crystallization temperature of A crystals whichhave the strongest line in powder X-ray diffraction using CuKα line inthe range of 27.6°-28.2°, by 25-100° C. compared to the case where no Zncomponent is incorporated. Furthermore, the incorporation sharpenscrystallization pattern of said crystals, and hence can preventoccurrence of residual carbon or swelling in formed glass-ceramic.

In occasions said Zn component may separate as, for example, gahnitecrystals. In consequence, excessive Zn component causes crystallizationof greatest part of Al component as B crystals, e.g., gahnite crystals,although consumption of the Al component for A crystals is preferred.Therefore, Zn component content in terms of ZnO is preferably 0.5-30 wt%, in particular, 0.5-25 wt %. ZnO can also be present in the amorphousportion.

Glass-ceramic according to the present invention preferably contains aboron (B) component as incorporated therein, to have a lowered softeningpoint and improved jointability with aluminum nitride sintered bodywhich is described later. Whereas, when a large amount of boron (B)component is contained, detrimental effects may be brought, such asincrease in hygroscopicity and reduction in chemical resistance, andpreferably the content in terms of B₂O₃ is in a range of 0.05-20 wt %,in particular, 0.05-18 wt %. B₂O₃ is present in amorphous portion ofglass-ceramic.

It is a general practice to blend a Ti and/or Zr component as acrystallization or nucreating agent, for crystallization ofcrystallizable component(s) in glass-ceramic. Ti and/or Zr component,however, increases thermal expansion coefficient of glass-ceramic, andits or their blending in a large amount is undesirable. Furthermore,when these components are contained in large amounts, they may causeseparation of CaO.TiO₂.SiO₂ crystals, CaO.ZrO₂.2TiO₂.SiO₂ cryastals orZrO₂.SiO₂ crystals to interfere with separation of the crystals havingan inherent strongest line in powder X-ray diffraction using CuKα linein the range of 2θ=27.6°-28.2°. According to my studies, by inclusion ofabove-listed CaO, Al₂O₃, SiO₂, ZnO and B₂O₃ as the constituentcomponents, it becomes possible to separate a sufficient amount ofcrystals in the glass-ceramic, in the complete absence of Ti and/or Zrcomponent. For approximating thermal expansion coefficients ofglass-ceramic and aluminum nitride sintered body, it is necessary tokeep blended amount of Ti and/or Zr component not higher than 10 wt % interms of oxide(s), in particular, not higher than 5 wt % in total, interalia, substantially zero.

According to the invention, the glass-ceramic is jointed with aluminumnitride sintered body. Generally a Pb component is blended in the glassto lower softening point of glass and facilitate its jointing withceramics. Pb, however, reacts with aluminum nitride at high temperaturesto evolve a gas, whereby causing swelling or the like in glass-ceramic.Therefore, less Pb component contained in the glass is preferred. Morespecifically, it must be no more than 5 wt % in terms of oxide thereof.It is preferred that substantially no Pb component is present in theglass.

It is permissible for the glass-ceramic according to the presentinvention to contain, besides those components so far described, anothercomponent or other components for the purpose of lowering softeningpoint of the glass or improving its jointability or adherability toaluminum nitride sintered body. As examples of such additionalcomponents, alkalu metals (Li, Na, K) or alkaline earth metals (Mg, Sr,Ba) may be named. When these components are blended in large amounts,however, deterioration in electrical properties (for example, dielectricconstant or electric resistance), reduction in chemical resistance orincrease in thermal expansion coefficient result.

Again, so long as the effects of the present invention are not impaired,other oxide component(s) may be blended.

It is preferred that the content of such component(s) other than CaO,Al₂O₃, SiO₂, ZnO, B₂O₃, PbO, TiO₂, ZrO₂ is not more than 7 wt % in termsof corresponding oxides. In particular, alkali metal component ispreferably not more than 2 wt %, and alkaline earth metal component, notmore than 5 wt %, both in terms of their respective oxides. It is moreconvenient that the sum of an alkali metal component and alkaline earthmetal component be not more than 5 wt %, even still better is that theglass is substantially free of these components. Absence of thesecomponents creates no problem.

Glass-ceramic according to the invention may further contain a fluorinecomponent which cannot be converted to an oxide, within a range notinterfering with the effects of the invention.

Considering the balance among such factors as ready availability ofstarting materials and ease of production which are discussed later;electric characteristics such as electrical resistance, dielectricconstant; jointability with aluminum nitride sintered body which also isobserved later; ready coincidence in thermal expansion coefficientsbetween the glass-ceramic and said sintered body; thermal resistance andchemical resistance; preferred composition of the glass-ceramicaccording to the present invention is as follows, in which all weightpercents are in terms of respective oxides: CaO: 5-25 wt %, Al₂O₃: 15-40wt %, SiO₂: 25-60 wt %, B₂O₃: 0.05-20 wt %, ZnO: 0.5-30 wt %, TiO₂+ZrO₂:0-5 wt %, PbO: 0-5 wt %, and other metal oxide(s): 0-7 wt %, (the totalof these components being 100 wt %); in particular, CaO: 8-25 wt %,Al₂O₃: 15-35 wt %, SiO₂: 33-55 wt %, B₂O₃: 0.05-18 wt % and ZnO: 0.5-25wt % (the total of these components being 100 wt %). Furthermore, in theoptimum composition, ZnO is 3-18 wt %.

The glass-ceramic of the present invention, which contains the crystalshaving the strongest line in powder X-ray diffraction using CuKα line inthe range of 2θ=27.6°-28.2° has electrical characteristics of highelectrical resistance and small dielectric constant, i.e., normally anelectric resistance of at least 1×10¹² Ω.cm and a dielectric constantnot higher than 8 at 1 GHz. As stated later, to allow an electriccircuit which is formed on glass-ceramic or aluminum nitride sinteredbody fully exhibits its characteristics, the glass-ceramic preferablyhas an electrical resistance of at least 1×10¹³ Ω.cm, in particular, atleast 1×10¹⁴ Ω.cm. Also its dielectric constant is preferably not morethan 7.5 at 1 GHz, in particular, not more than 7. Particularly suitableglass-ceramic for the jointed body of the present invention has anelectrical resistance of at least 1×10¹⁴ Ω.cm and a dielectric constantof not more than 7 at 1 Ghz.

Glass-ceramic of the present invention can be prepared by a method knownper se. More specifically, it can be prepared by preparing an amorphousglass of a composition capable of being crystallized to separate thecrystals having the strongest line in the range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line under heating and heating thesame to a prescribed temperature to crystallize the glass.

The amorphous glass has a softening point and crystallizationtemperature preferably not higher than 1100° C., in particular, nothigher than 1050° C., inter alia, not higher than 970° C. It is stillthe best that said point and temperature are not higher than 900° C.

Such an amorphous glass can be prepared by once fusing the startingmaterials which are formulated to give an above-described chemicalcomposition, and thereafter rendering it amorphous by such means asquenching to provide a glass.

As the starting materials to be used in the above production method ofsaid amorphous glass, oxides corresponding to the intended compositionof the glass can be named. Those oxides are not limited to simple oxidesbut complex oxides may also be used. Again as the starting materialsuseful in the above production method, carbonates and hydroxides canalso be suitably used besides oxides. Furthermore, halides such asfluorides, chlorides and the like; inorganic salts such as nitrates andsulfates; organic acid salts such as oxalates and citrates; organometalcompounds such as metal alkoxides; and hydrates of the foregoing canalso be used.

Specific examples of those compounds other than oxides include CaCO₃,Ca(OH)₂, calcium acetate, CaCl₂, CaF₂, Al(OH)₃, AlCl₃, AlF₃, magnesiumcarbonate, magnesium acetate, MgCl₂, MgF₂, H₃BO₃, tetraethyl silicateand the like. As SiO₂, natural product such as silica sand may also beused.

Describing the above production method in further details, thosestarting compounds are weighed to provide an intended composition interms of oxides and mixed, and fused at around 1200-1700° C. The fusedcomposition is quenched and vitrified by such means as flowing over awater-cooled metal plate. This glass can be confirmed to be amorphous byX-ray diffration analysis. The X-ray diffraction chart of the glass isbroad in the range of 2θ=18°-35° when CuKα line is used, showing apattern having a broad peak in the vicinity of 25° (FIG. 2).

This amorphous glass is crystallized under suitable heating conditionsto separate crystals having the strongest line in a range of2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line (A crystals)(FIGS. 4 and 5). Depending on selected composition and heatingconditions, in addition to A crystals, crystals having the strongestline in a range of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKαline (B crystals) are separated (FIGS. 6-9).

A jointed body according to the present invention is formed by jointingabove-described glass-ceramic with aluminum nitride sintered body.

As aluminum nitride sintered body which is used for the jointed body ofthe present invention, any known sintered bodies can be used without anylimitation, so long as their main component has a composition of AlN. Ascomponents other than AlN, for example, Y₂O₃, Yb₂O₃, Er₂O₃, Ho₂O₃ andcompounds of rare earth elements containing Sc, Y, Er, Yb, Dy, Ho, Gd,La and the like; and alkaline earth metal compounds such as CaO and SrO,can be used as sintering promotor; an alkali metal like Li₂O or siliconcompound such as SiO₂, Si₃N₄ or SiC can be used for lowering sinteringtemperature; and further metals such as Mo, W, V, Nb, Ta, Ti and thelike or compounds of those metals or carbon-containing compounds may beused for blackening the formed sintered bodies.

Aluminum nitride sintered body may have an as-sintered surface or thesurface may be given various treatments such as washing, honing,grinding or mirror-finishing, among which one meeting the purpose of usecan be selected for individual occasion.

Taking into consideration such factors as heat conductivity, chemicalresistance, thermal expansion coefficient, electrical characteristics,optical characteristics and ease of production of sintered body, use ofAlN sintered body substantially free of other components, or AlNsintered body containing 0.1-15 wt % of Y or Er compound in terms of therespective oxides (Y₂O₃, Er₂O₃) is preferred. In particular, use of AlNsintered body containing 0.5-10 wt % in terms of corresponding oxide ofY or Er compound is preferred.

Production method of a jointed body of the present invention in whichglass-ceramic is joined with aluminum nitride sintered body may be any,but the following method is particularly preferred.

That is, the method comprises forming a glass layer containing anamorphous glass (the starting glass) having a composition capable ofbeing crystallized under heating to separate the earlier describedcrystals having the strongest line in a range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line, on an aluminum nitridesintered body, and heating the resultant composite to a temperature notlower than the softening point of the starting glass, whereby jointingthe glass with the aluminum nitride sintered body. While it is possibleto crystallize to separate the crystals having the strongest line in arange of 2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line by aheating separately from the heating to effect the jointing, saidsimultaneous crystallization under the heating for the jointing is moreadvantageous for process design and is preferred. Namely, in theoccasion of heating an aluminum nitride sintered body on which thestarting glass layer is formed, by that single heating the jointed bodyof glass-ceramic and aluminum nitride sintered body can be produced byusing a heating temperature not lower than the softening point of thestarting glass and also not lower than the crystallization temperatureof the glass to separate crystals having the strongest line in the rangeof 2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line.

Such a heating temperature differs depending on individual startingglass composition, but 600-1100° C., in particular, 800-1050° C., arepreferred. It is still more convenient that a temperature within a rangeof 800-970° C. is used, inter alia, 800-900° C. Where the heatingtemperature is too low, the jointing or the crystallization tend tobecome insufficient. Conversely, heating at too high a temperature tendsto increase the crystal amount but at the same time, is disadvantageousin energy consumption. Furthermore, in the occasion of forming anelectric circuit layer as later described, such metals as Au, Ag, Cu andthe like which constitute said electric circuit layer are fused undersuch high temperature, and formation of adequate circuit pattern becomesdifficult.

Where the glass layer is formed of a multi-layered construction or aseparate heating is conducted in the later described occasion ofelectric circuit formation, i.e., when heating is conducted pluraltimes, crystallization does not necessarily occure at the first heatingonly for jointing an aluminum nitride sintered body with the glass, butit can progress during the subsequent heating(s).

It should be understood that the method of producing a jointed body ofthe present invention is not limited to the above, but if necessary sucha method comprising using as the starting glass a partially crystallizedglass and further advancing the crystallization under the heating forsoftening and joining; or a method comprising repeating glass pasteapplication, heating and softening cycle plural times and conducting alast heating for crystallization, may also be used.

Extent of crystallization can be confirmed by means of powder X-raydiffraction using CuKα line as aforesaid. According to the invention,crystals having the strongest line in a range of 2θ=27.6°-28.2° areseparated. Also another kind of crystals having the strongest line in arange of 2θ=36.6°-37.0° are also separated, said crystal having thestrongest line characteristic thereof at 2θ=36.6°-37.0° also shows asecond highest intensity line in a range of 2θ=31.0°-31.4°, as thecrystallization progresses.

For forming said starting glass layer on an aluminum nitride sinteredbody, any method known per se can be used.

Specifically, a method comprising pulverizing the starting glass, mixingit with an organic binder and solvent to form a paste, applying thepaste onto an aluminum nitride sintered body surface by such means asscreen printing, and heating the same to volatilize the organiccomponents is preferred.

In the occasion of forming the starting glass into a paste, averageparticle size of the glass powder is preferably 0.1-20 μm, inparticular, 0.3-10 μm, inter alia, 0.5-6 μm, from the viewpoint of easypaste production and favorable leveling property of the glass surfaceformed after the sintering for joining with aluminum nitride sinteredbody.

For the purpose of approximating thermal expansion coefficients ofglass-ceramic and aluminum nitride sintered body and of loweringdielectric constant or improving binder removing efficiency of theglass, it is effective to add a ceramic powder such as of Al₂O₃, SiO₂,Si₃N₄, SiC, AlN, mullite, spinel, cordierite and the like to thestarting glass paste as a filler. It is also permissible to add pigmentwhich contains a transition metal such as iron, cobalt, nickel orchromium, in an amount of a range not detrimental to the characteristicproperties of the glass, for example, not more than 5 wt % of atransition metal as converted to its oxide, to color the glass green,blue or brown. Generally spinel type pigments are preferred.

The joining or bonding strength between glass-ceramic and aluminumnitride sintered body in a jointed body of the present inventionpreferably is at least 25 Mpa, in particular, at least 35 Mpa, interalia, at least 50 Mpa, as measured by 90° C. perpendicular tensile test,from the standpoint of reliability and durability when the body is usedas a part of various devices.

In a jointed body of the present invention, an electric circuit ispreferably formed on the surface or inside of the glass-ceramic. It ispermissible that an electric circuit may be formed on the surface of thealuminum nitride sintered body.

As an electric circuit, any of known products containing conductors,resistor materials, dielectric materials and the like can be usedwithout any limitation. Methods of its formation again may be thoseknown ones.

For forming an electric circuit, low-resistance and low-melting pointmetals, e.g., Au, Ag and Cu; high-melting point metals, e.g., tungstenand molybdenum; and other various metal materials such as platinumgroup, nickel, chromium, cobalt, titanium, zirconium, tantalum, niobiumand their alloys; nitrides, carbides and silicates of those metals areused. Of those various materials, low-resistance materials such as Au,Ag, Cu and the like are most widely used. In order to avoide fusion ofthese metallic components, it is desirable that they are not heated attemperatures higher than 1100° C., in particular, higher than 1050° C.,at the time of the circuit formation.

As methods for forming electric circuit, known methods such as screenprinting using a metallic paste, electrolytic or non-electrolyticplating or thin film forming by means of sputtering or vapor depositioncan be used.

When an electric circuit is to be formed on surface of the aluminumnitride sintered body, a circuit or circuits can be formed on onesurface or plural surfaces (e.g., two surfaces facing with each other)of aluminum nitride sintered body, in advance of producing a jointedbody of glass-ceramic with aluminum nitride sintered body. In that case,the glass-ceramic may be joined in any manner as will or will not coverthe electric circuit on the aluminum nitride sintered body surface, orwill cover only a part of the electric circuit. Furthermore, theglass-ceramic can be joined in such a manner as will cover one surfaceonly of the aluminum nitride sintered body, or cover plural surfaces ofthe body. In the latter case, it is one of favorable embodiments to formelectric circuits on plural surfaces of an aluminum nitride sinteredbody, and to cover some of the circuits with glass-ceramic, leaving theremaining circuits uncovered. It is also possible to so effect thejoining as will cover only a part, not the entiety, of any one surface.

Glass-ceramic may also be joined not in contact with an electric circuitin the occasion of soldering surfaces of the material constituting anelectric circuit for preventing corrosion of said material, with theview to prevent fused solder from flowing into the parts not requiringsoldering.

When an electric circuit is to be formed on the glass-ceramic surface,it can be performed in the manner similar to above-described methods forforming an electric circuit or circuits on aluminum nitride sinteredbody surface. As a method for forming an electric circuit inside of theglass-ceramic, the one comprising first forming a layer of a substancecapable of forming an electric circuit under heating on the surface ofthe starting glass, heating the laminate to convert it to aglass-ceramic with a surface on which an electric circuit layer isformed, then further forming a glass layer on said electric circuitlayer to cover the latter, heating the whole once again to integrate theglass, and repeating the above-described procedures. It is preferred forthus prepared glass laminate to be so well integrated that the jointedportions are fused and visually indistinguishable. In certain cases,however, the integration is incomplete, allowing confirmation of eachglass layer and junctions therebetween. This invention also encompassessuch an embodiment.

In the occasion of laminating glass at multiple stages, glasses ofdifferent compositions may be used for individual layers. For example,for the layer contacting with aluminum nitride sintered body, a glassexhibiting high jointability and having a low softening point can beused, while for the layer contacting the atmospheric air, a glass ofhigh chemical resistance can be used. Furthermore, within an extent notimpairing the effects of the present invention, a glass not containingthe crystal having the strongest line in the range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line can be concurrently used. Anexample of such a case is illustrated as over-glass 4 in later discussedFIG. 20.

Among these methods for forming electric circuit, furthermore, apreferred embodiment comprises applying a known conductive metallicpaste onto an aluminum nitride sintered body surface and/or onto a glasslayer formed of a glass paste which contains the amorphous startingglass, by such means as screen printing, and heating the laminate at800-970° C. to simultaneously effect conversion of the amorphous glasspaste to glass-ceramic, joining the glass-ceramic with the aluminumnitride sintered body, and conversion of the conductive paste to anelectric circuit.

In the above-described case of adopting multi-layered electric circuitsand glass-ceramic construction, the glass-ceramic functions as aninsulation layer between every two electric circuits. Thickness of theglass-ceramic layer serving as an insulation layer is preferably 1-300μm, in particular, 3-100 μm, inter alia 5-70 μm, per layer, for assuringgood electrical insulation and facilitating formation of via hole(s)electrically connecting electric circuit layers and formation of uniformthickness.

The present invention also provides a method as above-described, whichforms glass.ceramic, aluminum nitride sintered body and electriccircuit(s) by heating.

In this case, the starting amorphous glass to be converted toglass-ceramic does not necessarily contain Zn component, it beingsufficient for obtaining the effects of the invention that it is capableof separating under heating a crystal having the strongest line in therange of 2θ=27.6°-28.2° in powder X-ray diffraction using CuKα l and issubstantially amorphous, containing in total not more than 10 wt % of Ticomponent and Zr component in terms of respective oxides, and not morethan 5 wt % of Pb component in terms of its oxide. Needless to say, theamorphous glass preferably contains 0.5-30 wt % of Zn component, so thatthe heating temperature for the jointed body production can be lowered.

In a preferred embodiment of the jointed body according to theinvention, which is formed of glass-ceramic and aluminum nitridesintered body, the glass-ceramic contains 30-80 wt % of crystallineportion, 60-90 wt % of said crystalline portion being the crystalshaving the strongest line in a range of 2θ=27.6°-28.2° in powder X-raydiffraction using CuKα line, and 10-40 wt % of said crystalline portionbeing the crystals having the strongest line in the range of2θ=36.6°-37.0° in powder X-ray diffraction using CuKα line; saidglass-ceramic has a composition composed of CaO: 8-25 wt %, Al₂O₃: 15-35wt %, SiO₂: 33-55 wt %, ZnO: 0.5-25 wt % and B₂O₃: 0.05-18 wt %, being aCaO—Al₂O₃—SiO₂—B₂O₃—ZnO glass-ceramic substantially free of othercomponent; an average jointing strength at the glass-ceramic-aluminumnitride sintered body interface, as measured by 90° perpendiculartensile test, is at least 35 MPa; and electric circuits are formed inmulti-layers on the surface and/or inside of the glass-ceramic.

A particularly preferred embodiment is a jointed body in which thecrystalline portion of the glass-ceramic is 40-70 wt % wherein anorthitecrystals occupying 70-90 wt % and gahnite crystals occupying 10-30 wt %;the glass-ceramic has an electric resistance of at least 1×10¹⁴ Ω.cm anddielectric constant not higher than 7 at 1 GHz; the average jointingstrength of the glass-ceramic and aluminum nitride sintered body attheir interface, as measured by 90° perpendicular tensile test is atleast 50 MPa; and electric circuits are formed in multi-layers on thesurface and/or inside of the glass-ceramic.

FIG. 20 shows an example of a circuit substrate. Referring to FIG. 20, athree layered glass-ceramic 1 is formed on an aluminum nitride sinteredsubstrate 2. At inside and on surface of the glass-ceramic and onsurfaces of the aluminum nitride sintered substrate, wiring conductors 3are formed. For these wiring conductors, low resistance material madechiefly of Cu, Ag and Au is useful. Besides, cover glass 4 forprotecting the wiring conductors and via 6 for conductivity are formed.This circuit substrate carries semiconductor chip 5 and chip parts 7such as resistor and capacitor.

Jointed bodies of the present invention are not limited to the oneillustrated on FIG. 20. For example, the glass layer may be formed ofone, two, or four or more layers. Also semiconductor chip mounting ispreferably conducted directly on aluminum nitride sintered sabstratewithout a glass layer intervening, as shown on FIG. 20 for better heatspreading, while it is possible to mount it through a thin glass layerwhere circuit design requires it. The thickness of the glass layer insuch an occasion is preferably not more than 100 μm. The semiconductorchip can be mounted not on the glass layer side as shown in FIG. 20, buton the opposite side.

In the present invention, the glass-ceramic containing a crystal havingthe strongest line in the range of 2θ=27.6°-28.2° in powder X-raydiffraction using CuKα line exhibits, besides chemical resistance,excellent oxidation resistance, plasma etching resistance and the like,and upon being joined with aluminum nitride sintered body, prevents thebody from direct exposure to severe environments and contributes toimprovements in chemical resistance (in particular, alkali resistance orcorrosion resistance by molten salts), oxidation resistance (inparticular, corrosion resistance in an oxidizing atmosphere at hightemperatures not lower than 600° C.) and plasma etching resistance (inparticular, resistance of semiconductor production apparatus tocorrosion by plasma gas containing corrosive elements such as chlorineand fluorine) of the aluminum nitride sintered body. Jointed bodies ofglass-ceramic and aluminum nitride sintered body according to thepresent invention, therefore, are applicable not only to above circuitsubstrate but also to mechanical parts or high temperature structuralmaterial for heater or the like or tooling for semiconductor-producingapparatus.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a comparison of powder X-ray diffraction chart of the glassobtained by heating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 900° C.for 20 minutes in Example 1, with JCPDS cards.

FIG. 2 is a powder X-ray diffraction chart of CaO—Al₂O₃—SiO₂—B₂O₃—ZnOamorphous glass which was obtained in Example 1.

FIG. 3 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 800° C. for 20minutes in Example 1.

FIG. 4 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 830° C. for 20minutes in Example 1.

FIG. 5 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 840° C. for 20minutes in Example 1.

FIG. 6 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 850° C. for 20minutes in Example 1.

FIG. 7 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 875° C. for 20minutes in Example 1.

FIG. 8 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 900° C. for 20minutes in Example 1.

FIG. 9 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 1000° C. for 20minutes in Example 1.

FIG. 10 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—MgO amorphous glass at 850° C. for 20minutes in Referential Example 1.

FIG. 11 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—MgO amorphous glass at 900° C. for 20minutes in Referential Example 1.

FIG. 12 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—MgO amorphous glass at 1000° C. for 20minutes in Referential Example 1.

FIG. 13 is a powder X-ray diffraction chart of a CaO—Al₂O₃—SiO₂—B₂O₃—ZnOamorphous glass obtained in Example 2.

FIG. 14 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 800° C. for 20minutes in Example 2.

FIG. 15 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 850° C. for 20minutes in Example 2.

FIG. 16 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 875° C. for 20minutes in Example 2.

FIG. 17 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 900° C. for 20minutes in Example 2.

FIG. 18 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 950° C. for 20minutes in Example 2.

FIG. 19 is a powder X-ray diffraction chart of the glass obtained byheating CaO—Al₂O₃—SiO₂—B₂O₃—ZnO amorphous glass at 1000° C. for 20minutes in Example 2.

FIG. 20 is a type diagram of an example of jointed body formed ofglass-ceramic and aluminum nitride sintered body.

EXAMPLES AND REFERENTIAL EXAMPLES

Hereinafter the present invention is explained more specifically,referring to working examples, it being understood that the presentinvention is not limited to these examples.

Example 1

Starting materials were mixed in a ball mill by dry system, to give 60 gof a starting blend consisting of CaO: 15 wt %, Al₂O₃: 24 wt %, SiO₂: 42wt %, B₂O₃: 8 wt % and ZnO: 11 wt %. This blend was placed in a platinumcrucible and fused at 1600° C. The starting materials used were oxidepowders, excepting that CaCO₃ powder was used as the CaO source. Thefusion fluid was let flow on water-cooled stainless steel plate andquenched to provide a glass. Upon examining by powder X-ray diffraction,this glass was found amorphous. Its diffraction chart is shown as FIG.2.

The glass was then pulverized in a ball mill to an average particle sizeof 5 μm, and the resulting powder was heated in an alumina crucibles ata temperature rise rate of 20° C./min, to be maintained at temperaturesof 800° C., 830° C., 840° C., 850° C., 875° C., 900° C. and 1000° C.,respectively, all for 20 minutes. After cooling, compositions of theheated glass powders were examined by powder X-ray diffraction. Theglass heated at 800° C. (FIG. 3) was not crystallized, but in the oneheated at 830° C. separation of crystals having the strongest line inthe range of 2θ=27.6°-28.2° could be confirmed (FIG. 4). At 840° C., thecrystallization progressed (FIG. 5), and at 850° C., separation ofcrystals having the strongest line in the range of 2θ=36.6°-37.0° wasconfirmed and at the same time, crystallized amount of the crystalshaving the strongest line in the range of 2θ=27.6°-28.2° rapidlyincreased (FIG. 6). FIGS. 7-9 are powder X-ray diffraction charts of thesame glass heated at 875° C., 900° C. and 1,000° C., respectively.

Intensities of the strongest line (diffraction lines in the vicinity of2θ=27.9°-28.0°) were compared to reveal that the extent ofcrystallization did not appreciably vary among those heated at 850° C.,875° C. and 900° C., and that the crystallization rapidly took place ataround 850° C.

Separation of the crystals having the strongest line in the range of2θ=36.6°-37.0° was not observed under the heating at 830° C. and 840°C., but a small amount of the crystals were observed at 850° C., furthercrystallization advancing at 875° C.-900° C.

Upon comparing these crystals with JCPDS, the crystals having thestrongest line in the range of 2θ=27.6°-28.2° were identified to beanorthite crystals, and those having the strongest line in the range of2θ=36.6°-37.0°, to be gahnite crystals (FIG. 1). Separation of no othercrystal was confirmed. In FIGS. 6-9, the peaks attributable to gahnitecrystals are marked with circles. All other diffraction peaks areattributable to anorthite crystals.

Diffraction intensity, R and amount of crystallization of each of theseglasses in powder X-ray diffraction using CuKα line are shown in Table1.

According to differential thermal analysis (heating at a temperaturerise rate of 20° C./min.), the crystallization ceased at 925° C., whichapproximately coincides with the results of above X-ray diffraction. Theamount of crystals in the crystallized glass under heating at 900° C.was calculated to be 59.36 wt % by the earlier described method, inwhich anorthite crystals occupied 47.55 wt % and gahnite crystals, 11.81wt %. The rest was amorphous glass matrix. The amount of crystals in theglass-ceramic heated at 830° C. was calculated to be 2.24 wt % by theearlier described method, which all was attributable to anorthitecrystals, the rest being amorphous glass matrix. For all the samples,X-ray diffraction was conducted with PW 1830 model full automatic powderX-ray diffractiometer manufactured by Philips Co., using Cu as theanticathode and the Kα line yielded under applied voltage and current of40 KV and 40 mA. Samples for the X-ray diffraction were powderized andtightly filled in 15×20 mm rectangular depression formed in a glassholder. The given X-ray intensity values are the count numbers obtainedby subtracting the count intensity of background of X-ray from directlycounted intensity.

Compositions of the amorphous portions were as follows: in theglass-ceramic with crystalline content of 59.36 wt %, CaO: 5.44 wt %,SiO₂: 21.45 wt %, B₂O₃: 8 wt % and ZnO: 5.76 wt %; and in theglass-ceramic with crystalline content of 2.235 wt %, CaO: 14.55 wt %,Al₂O₃: 23.18 wt %, SiO₂: 41.04 wt %, B₂O₃: 8 wt % and ZnO: 11 wt %.

The glass powder pulverized to an average particle size of 5 μm afterthe quenching was press-molded under a pressure of 300 kgf/cm², and themolded body was heated in the air at 900° C. for 20 minutes to provide aglass-ceramic molded body, in three different configurations of 1×1×60mm square rod, 5×5×50 mm prism and 30 mm in diameter×2 mm in thicknessdisc. Dielectric constant and direct-current electric resistance at highfrequency of those sintered bodies were measured underconstant-temperature and constant-humidity conditions of 20° C. and 60Rh %. The dielectric constant was measured by perturbation method using1×1×60 mm test specimens, with the results of 6.6 at 1 GHz, 6.7 at 3 GHzand 6.4 at 10 GHz, which were less compared to aluminum nitride sinteredbody. Thermal expansion coefficient was measured with 5×5×50 mm testspecimens, which was 4.8×10⁻⁶/° C. at 100-500° C. Direct-currentelectric resistance was measured with the disc test specimens, with theresult showing high insulation property, as 5.9×10¹⁵ Ω.cm after anapplied voltage of 500 V for 1 minute.

Then 10 g of the glass powder which was quenched and pulverized to anaverage particle size of 5 μm as above was mixed with 4 g of α-terminalas solvent and 0. 15 g of ethyl cellulose as binder, to form a paste.This paste was applied onto a surface of 40′ 45′ 0.635 mm aluminumnitride sintered substrate (Tokuyama Corporation, SH30™) by screenprinting method. After drying off, the paste was heated at a temperaturerise rate of 20° C./min. and at 900° C. for 20 minutes, either in theair or in a N₂ atmosphere. The resulting glass had a thickness of 20 μm.In both of the products obtained by sintering in the air or in N₂atmosphere and subsequent quenching, the glass-ceramic and aluminumnitride sintered body were intimately jointed and no crack or peelingwas observed. The jointed bodies were not warped. Then sintering wasrepeated 4 times under identical conditions, but no defect in jointedportions was caused. The sample sintered in N₂ atmosphere did not show atendency for blackening in the glass or swelling or foaming phenomenon.

Using the remainder of the substrate the glass paste on which had beendried, further a copper metal paste containing pure copper powder as itssolid component (Kyoto Elex Co., DD 3200A™) was applied on the glasspaste in a disc form of 2.5 mm in diameter and 13 μm in thickness byscreen printing method and dried. These were sintered at 900° C. for 20minutes in N₂ atmosphere, together with the dry glass paste. The copperpaste was converted to sintered copper metal, onto which a 42% Ni—Fealloy rod of 1.2 mm in diameter was soldered and subjected to 90°perpendicular tensile test. The average of ten measurements at differentsites of the copper metal portions was 56 MPa. The minimum value was 29MPa and the maximum value was 80 MPa. When disruption mode in thisstrength test was examined, the copper metal portion was broken inlow-strength samples. In high-strength samples, either inside of theglass-ceramic or inside of the aluminum nitride sintered body wasbroken, but at none of the measurement site breakage occurred at aroundthe interface between the glass-ceramic and aluminum nitride sinteredbody. Thus it was confirmed that the joining or bonding of theglass-ceramic with aluminum nitride sintered body was considerablystrong.

Referential Example 1

An amorphous glass having a composition of CaO: 16 wt %, Al₂O₃: 27 wt %,SiO₂: 44 wt %, B₂O₃: 9 wt % and MgO: 4 wt % was prepared similarly toExample 1, and the amorphous glass was heated at the varioustemperatures of 800° C., 850° C., 900° C. and 1,000° C., for 20 minutes.Their X-ray diffraction patterns after the heating were shown in FIGS.10-12, respectively.

X-ray intensity values at 2θ=27.6°-28.2° of these heated glasses areshown in Table 1. Crystals separated in this glass were invariablyanorthite crystals.

As is clear from Table 1, the glass containing a Zn component of Example1 separated anorthite crystals at lower temperatures than the glass notcontaining Zn component used in Referential Example 1. That is, in theglass of Example 1, anorthite crystals started to separate at 830° C.,the crystals grew at 840° C. and rapidly increased under heating at 850°C. The crystal amount at 850° C. was nearly the same to that at 1000° C.On the other hand, in the glass of the Referential Example notcontaining a Zn component, the amount of anorthite crystals under 900°C. heating was equivalent to that under 840° C. in Example 1, thedifference being by about 60° C. Taking also into consideration thedifferential thermal analysis data, where a Zn component was blended,the crystallization temperature was lowered by 25-100° C.

TABLE 1 Example 1 Example 2 Referential Amount of Amount of Example 1Crystals/wt % Crystals/wt % X-Ray Count Heating X-Ray Count Number Total(anorthite X-Ray Count Number Total (anorthite Number ConditionAnorthite (gahnite) R crystals crystals) Anorthite (gahnite) R crystalscrystals) anorthite No heating amorphous — — amorphous — — amorphous800° C. × 20 min. amorphous — — amorphous — — amorphous 830° C. × 20min. 55  (0) 0 2.235  (2.235) — — — — 840° C. × 20 min. 346  (0) 0 14.06(14.06) — — — — 850° C. × 20 min. 1116  (90) 0.0806 47.77 (45.36) 76 (0) 0 3.733  (3.733) amorphous 875° C. × 20 min. 1129 (357) 0.316255.44 (45.88) 320  (0) 0 15.72 (15.72) — 900° C. × 20 min. 1170 (441)0.3769 59.36 (47.55) 751  (0) 0 36.89 (36.89) 331 950° C. × 20 min. — —— 740 (53) 0.0720 38.08 (36.35) — 1000° C. × 20 min.  1037 (412) 0.397353.39 (42.14) 999 (56) 0.0563 50.72 (49.07) 1197

Example 2

An amorphous glass having a composition of CaO: 15 wt %, Al₂O₃: 19 wt %,SiO₂: 42 wt %, B₂O₃: 12 wt % and ZnO: 12 wt % was prepared in the mannersimilar to Example 1, which was maintained at various temperatures of800° C., 850° C., 875° C., 900° C., 950° C. and 1,000° C., for 20minutes. The amounts of crystals in the respective glass-ceramics wereexamined, whereby it could be confirmed that no crystallization occurredat 800° C. (FIG. 14), but at 850° C. anorthite crystals started toseparate (FIG. 15). At 875° C. anorthite crystallization progressed(FIG. 16) and at 900° C. the crystallization nearly terminated (FIG.17). According to differential thermal analysis (heating at atemperature rise rate of 20° C./min.), the crystallization temperatureof the glass-ceramic of this Example was 998° C.

On the other hand, no gahnite crystal was observed during the 900° C.heating or at lower temperatures, but at 950° C. a minor separation tookplace (FIG. 18) and even at 1000° C. its amount did not increaseappreciably (FIG. 19).

The amount of crystals in the glass-ceramic after the 1000° C. heatingwas calculated to be 50.89 wt % by the earlier described method, inwhich the amount of anorthite crystals was 49.07 wt % and that ofgahnite crystals was 1.82 wt %, the rest being amorphous glass matrix.Also the amount of crystals in the glass-ceramic after the 850° C.heating was calculated to be 3.73 wt % by the earlier described method,which all was anorthite crystals. The remaining part was amorphous glassmatrix.

The composition of the amorphous portion was: in the glass-ceramic withthe crystal content of 50.89 wt %, CaO: 5.11 wt %, SiO₂: 20.81 wt %,B₂O₃: 12 wt % and ZnO: 11.19 wt %; and with the glass-ceramic with thecrystal content of 3.733 wt %, CaO: 14.25 wt %, Al₂O₃: 17.63 wt %, SiO₂:40.40 wt %, B₂O₃: 12 wt % and ZnO: 12 wt %.

FIG. 13-19 show the powder X-ray diffraction charts at the respectiveheating temperatures, and Table 1 shows the X-ray intensities andcrystal amounts.

The amorphous glass was press-molded at 900° C. similarly to Example 1to provide a glass-ceramic molded body, and its dielectric constant anddirect-current electric resistance were measured. The dielectricconstant was 6.5 at 1 GHz, 6.7 at 3 GHz and 6.6 at 10 GHz, which wereless than those of aluminum nitride sintered body; and thedirect-current electric resistance was 7.7×10¹⁵ Ω.cm, exhibiting highelectric insulation. The thermal expansion coefficient at 100-300° C.was 4.5×10⁻⁶/° C., and that at 100-500° C. was 4.9×10⁻⁶/° C.

Then its jointability with aluminum nitride sintered body was examinedin the manner similar to Example 1. The results were: in both of theproducts sintered in the air and in N₂ atmosphere the glass-ceramic andaluminum nitride sintered bodies were intimately joined after quenchingand no cracking or peeling was observed. The jointed bodies also werenot warped. Thereafter the sintering was repeated 4 times underidentical conditions, without developing any joining defect. The samplessintered in N₂ atmosphere did not show any blackening tendency in theglass-ceramic or swelling or foaming phenomenon. The thickness of theglass layer after sintering was 40 μm.

Jointed bodies were prepared in the identical manner with Example 1,except that the amorphous glass which was formed in this Example and ametallic paste formed of Ag/Pt powder containing 1 wt % of Pt as thesolid component (Kyoto Elex Co.) were used, and the products' 90°perpendicular tensile test was conducted. The average of tenmeasurements at different sites of the metal portion was 54 MPa; theminimum value was 26 MPa and the maximum value was 74 MPa. Whendisruption mode in this tensile test was examined, the metal portion wasbroken in low-strength samples. In high-strength samples, either insideof the glass-ceramic or inside of the aluminum nitride sintered body wasbroken, but at none of the measurement site breakage occurred at aroundthe interface between the glass-ceramic and aluminum nitride sinteredbody. Thus it was confirmed that the jointing strength of theglass-ceramic with aluminum nitride sintered body was considerablystrong.

Referential Example 2

With the view to examine the influence of Pb component content in theglass, an amorphous glass composed of CaO: 15 wt %, AM₂O₃: 24 wt %,SiO₂: 42 wt %, B₂O₃: 7.6 wt %, ZnO: 11 wt %; and PbO: 0.4 wt %; andanother amorphous glass composed of CaO: 13 wt %, Al₂O₃: 21 wt %, SiO₂:38 wt %, B₂O₃: 7.1 wt %, ZnO: 10 wt % and PbO: 10. 9 wt % were prepared,which were joined with aluminum nitride sintered body by the methodsimilar to that used in Example 1.

The glass which contained 0.4 wt % of PbO could be jointed with aluminumnitride sintered body without any problem, while in the glass containing10.9 wt % of PbO a large extent of swelling and foaming occurred in theglass, and when the jointed portion was touched with forceps, theglass-ceramic and aluminum nitride sintered body readily separated.

Referential Example 3

For examining the influence of Ti component and Zr component contents inthe glass, an amorphous glass composed of CaO: 19 mass %, Al₂O₃: 20 mass%, SiO₂: 32 mass %, B₂O₃: 9 mass % and TiO₂: 20 mass %; and anotheramorphous glass composed of CaO: 19 mass %, Al₂O₃: 11 mass %, SiO₂: 27mass %, B₂O₃: 8 mass %, ZrO₂: 10 mass % and TiO₂: 25 mass % wereprepared, which were heated at 900° C. for 20 minutes to be converted toglass-ceramics. The glass containing 20 mass % of TiO₂ had a thermalexpansion coefficient of 5.8×10⁻⁶/° C., and the glass containing 35 mass% in total of TiO₂ plus ZrO₂ had that of 6.2×10⁻⁶/° C., the valuesconsiderably higher than the thermal expansion coefficient, 4.5×10⁻⁶/°C., of aluminum nitride sintered body.

Example 3

A 40×45×0.635 mm aluminum nitride sintered substrate (TokuyamaCorporation, SH 30™) with an open through-hole of 0.4 mm in diameterfrom the front to the back of the substrate was prepared. A commerciallyavailable copper-containing paste (Kyoto Elex Co., DD3200B™) wasadjusted to a low viscosity with α-terpineol, and applied to saidthrough-hole and dried. This through-hole and the conductor formedthereon correspond to the via 6 for conductivity formed in aluminumnitride substrate 2 in FIG. 20. Further on the top and bottom surfacesof the substrate, prescribed electric circuits were applied with a pasteof which viscosity was not adjusted, by means of screen printing anddried. These electric circuits correspond to wiring conductors 3 onaluminum nitride sintered substrate shown in FIG. 20. The aluminumnitride sintered substrate on which the conductor paste was printed anddried was sintered in N₂ atmosphere at 900° C. for 20 minutes.

The Cu conductors on the aluminum nitride sintered substrate surfacesafter the sintering had a thickness of 13 μm. On the sintered substratesurface, the glass paste which was prepared in Example 1 was applied byscreen printing method, dried and sintered in N₂ atmosphere at 900° C.for 20 minutes. Onto the glass after the sintering, further the glasspaste was screen printed in the identical pattern and dried, on which aprescribed electric circuit was screen printed using said Cu paste anddried, followed by a sintering in N₂ atmosphere at 900° C. for 20minutes. The glass layers applied two times separately each had athickness of 40 μm after the sintering. In this operation, a cavity wasformed at prescribed position at the time of glass paste printing, andby filling the cavity with the Cu paste and sintering, a continuous viafor conductivity was formed in the formed glass. Repeating similarprocedures, an electric circuit as illustrated by FIG. 20 in which athree-layered glass layer was formed, was obtained.

If necessary an over-glass 4 or Au plating is applied on the Cuconductor portion on the surface of this circuit substrate. Then asemiconductor chip 5 was mounted, and the semiconductor chip and thecircuit substrate were electrically connected by wire bonding or likemeans. Further, if necessary chip parts 7 such as a condenser, resistorand the like may optionally be mounted.

Example 4

An aluminum nitride sintered circuit on which conductor paste wasprinted, dried and sintered was obtained in the manner similar toExample 3, except that the sintering time was 10 minutes.

Onto the surface of the sintered substrate, a glass paste prepared fromthe amorphous glass of Referential Example 1 was applied by screenprinting method, dried and sintered in N₂ atmosphere at 900° C. for 10minutes. Further on the sintered glass surface, the glass paste wasscreen printed in the identical pattern and dried, and a prescribedelectric circuit was screen printed thereon using said Cu paste anddried, followed by sintering in N₂ atmosphere at 900° C. for 10 minutes.The glass layers applied two times separately each had a thickness of 40μm. In this operation, a cavity was formed at prescribed position at thetime of glass paste printing, and by filling the cavity with the Cupaste and sintering, a via for conductivity was formed in the formedglass layer. Repeating similar procedures, a circuit substrate asillustrated by FIG. 20 in which a three-layered glass layer was formed,was obtained.

What is claimed is:
 1. A joined body of glass-ceramic consisting ofcrystalline portion and amorphous portion with aluminum nitride sinteredbody, which is characterized in that said crystalline portion iscomposed mainly of crystals having the strongest line in a range of2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line, and saidglass-ceramic has a composition containing 0.5-30% by weight of Zncomponent in terms of oxide, not more than 10% by weight in total of Ticomponent and Zr component in terms of respective oxides and not morethan 5% by weight of Pb component in terms of oxide.
 2. A joined bodyaccording to claim 1, in which the glass-ceramic has a compositionformed of: CaO: 5-25% by weight, Al₂O₃: 15-40% by weight, SiO₂: 25-60%by weight, ZnO: 0.5-30% by weight, B₂O₃: 0.05-20% by weight, TiO₂+ZrO₂:0-5% by weight, PbO: 0-5% by weight, and other metal oxide or oxides:0-7% by weight in terms of corresponding oxides (provided that the sumof above components is 100% by weight).
 3. A jointed body according toclaim 1, in which the glass-ceramic has a composition formed of: CaO:8-25% by weight, Al₂O₃: 15-35% by weight, SiO₂: 33-55% by weight, ZnO:0.5-25% by weight and B₂O₃: 0.05-18% by weight, in terms ofcorresponding oxides (provided that the sum of above components is 100%by weight).
 4. A joined body according to claim 1, which ischaracterized in that the crystals having the strongest line in a rangeof 2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line areanorthite crystals.
 5. A joined body according to claim 1, in which thecrystals contained in the crystalline portion of glass-ceramic comprisethose having the strongest line in a range of 2θ=27.6°-28.2° in powderX-ray diffraction using CuKα line and those having the strongest line ina range of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKα line.6. A joined body according to claim 5, in which the crystals having thestrongest line in a range of 2θ=27.6°-28.2° in powder X-ray diffractionusing CuKα line are anorthite crystals and those having the strongestline in a range of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKαline are gahnite crystals.
 7. An electric circuit substrate made of ajoined body formed by joining glass-ceramic consisting of crystallineportion and amorphous portion with aluminum nitride sintered body, inwhich the crystalline portion is composed mainly of crystals having thestrongest line in a range of 2θ=27.6°-28.2° in powder X-ray diffractionusing CuKα line, and said glass-ceramic has a composition containing0.5-30% by weight of Zn component in terms of oxide, not more than 10%by weight in total of Ti component and Zr component in terms ofrespective oxides and not more than 5% by weight of Pb component interms of oxide.
 8. An electric circuit substrate in which an electriccircuit or circuits are formed in at least one surface or inside of theglass-ceramic or on surface of the aluminum nitride sintered body, in ajoined body as described in claim
 1. 9. A method of preparing a joinedbody of glass-ceramic with aluminum nitride sintered body, which ischaracterized by forming a glass layer on an aluminum nitride sinteredbody, said glass layer containing a substantially amorphous glass havinga composition containing 0.5-30% by weight of Zn component in terms ofoxide, not more than 10% by weight in total of Ti component and Zrcomponent in terms of respective oxides and not more than 5% by weightof Pb component in terms of oxide; joining said glass layer with thealuminum nitride sintered body by heating them to a temperature notlower than the softening point of the amorphous glass, and separatingcrystals having the strongest line in a range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line in said glass by said heating.10. A preparation method according to claim 9, wherein the amorphousglass has a composition formed of: CaO: 5-25% by weight, Al₂O₃: 15-40%by weight, SiO₂: 25-60% by weight, ZnO: 0.5-30% by weight, B₂O₃:0.05-20% by weight, TiO₂+ZrO₂: 0-5% by weight, PbO: 0-5% by weight, andother metal oxide or oxides: 0-7% by weight in terms of correspondingoxides (provided that the sum of above components is 100% by weight).11. A preparation method according to claim 9, wherein the amorphousglass has a composition formed of: CaO: 8-25% by weight, Al₂O₃: 15-35%by weight, SiO₂: 33-55% by weight, ZnO: 0.5-25% by weight and B₂O₃:0.05-18% by weight, in terms of corresponding oxides (provided that thesum of above components is 100% by weight).
 12. A preparation methodaccording to claim 9, which is characterized by separating crystalshaving the strongest line in a range of 2θ=27.6°-28.2° in powder X-raydiffraction using CuKα line and crystals having the strongest line in arange of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKα line. 13.A method of preparing a joined body of glass-ceramic on which anelectric circuit or circuits are formed, with aluminum nitride sinteredbody, which is characterized by forming a glass layer on an aluminumnitride sintered body, said glass layer containing a substantiallyamorphous glass which is capable of crystallizing under heating, thecrystals having the strongest line in a range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line and containing not more than10% by weight in total of Ti component and Zr component in terms ofcorresponding oxides and not more than 5% by weight of Pb component interms of oxide, also forming a substance which is capable of forming anelectric circuit layer under heating, on said glass layer and/or on thealuminum nitride sintered body, and thereafter heating the system attemperatures of 600-1100° C., whereby mutually joining the layers of theglass, aluminum nitride sintered body and electric circuit andseparating said crystals in the glass layer to convert it glass-ceramic.14. A preparation method according to claim 13, in which crystals havingthe strongest line in a range of 2θ=27.6°-28.2° in powder X-raydiffraction using CuKα line and crystals having the strongest line in arange of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKα line areseparated in the occasion of heating.
 15. A preparation method accordingto claim 13, in which the heating temperature is 800-970° C.
 16. Ajoined body according to claim 2, which is characterized in that thecrystals having the strongest line in a range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line are anorthite crystals.
 17. Ajoined body according to claim 3, which is characterized in that thecrystals having the strongest line in a range of 2θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line are anorthite crystals.
 18. Ajoined body according to claim 2, in which the crystals contained in thecrystalline portion of glass-ceramic comprise those having the strongestline in a range of 2θ=27.6°-28.2° in powder X-ray diffraction using CuKαline and those having the strongest line in a range of 2Θ=36.6°-37.0° inpowder X-ray diffraction using CuKα line.
 19. A joined body according toclaim 3, in which the crystals contained in the of glass-ceramiccomprise those having the strongest line in a range of 2Θ=27.6°-28.2° inpowder X-ray diffraction using CuKα line and those having the strongestline in a range of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKαline.
 20. An electric circuit substrate in which an electric circuit orcircuits are formed in at least one surface or inside of theglass-ceramic or on surface of the aluminum nitride sintered body, in ajoined body as described in claim
 2. 21. An electric circuit substratein which an electric circuit or circuits are formed in at least onesurface or inside of the glass-ceramic or on surface of the aluminumnitride sintered body, in a joined body as described in claim
 3. 22. Anelectric circuit substrate in which an electric circuit or circuits areformed in at least one surface or inside of the glass-ceramic or onsurface of the aluminum nitride sintered body, in a joined body asdescribed in claim
 4. 23. An electric circuit substrate in which anelectric circuit or circuits are formed in at least one surface orinside of the glass-ceramic or on surface of the aluminum nitridesintered body, in a joined body as described in claim
 5. 24. An electriccircuit substrate in which an electric circuit or circuits are formed inat least one surface or inside of the glass-ceramic or on surface of thealuminum nitride sintered body, in a joined body as described in claim6.
 25. A preparation method according to claim 10, which ischaracterized by separating crystals having the strongest line in arange of 2θ=27.6°-28.2° in powder X-ray diffraction using CuKα line andcrystals having the strongest line in a range of 2θ=36.6°-37.0° inpowder X-ray diffraction using CuKα line.
 26. A preparation methodaccording to claim 11, which is characterized by separating crystalshaving the strongest line in a range of 2θ=27.6°-28.2° in powder X-raydiffraction using CuKα line and crystals having the strongest line in arange of 2θ=36.6°-37.0° in powder X-ray diffraction using CuKα line. 27.A preparation method according to claim 14, in which the heatingtemperature is 800-970° C.